Toner replenishment based on writer current

摘要

A method and apparatus for replenishing toner based on the electric current used over time by the exposure subsystem. Toner take-out for each image is estimated by measuring the current used by the exposure system, subtracting the quiescent current, integrating over a page or frame, and multiplying by a predetermined value that indicates the amount of toner required by the image, based on the average current used for the exposure and other process parameters. These calculations are done either in hardware or in software. The replenishment system is used to add the correct amount of toner to the developer station to maintain the toner concentration at an approximately constant aim value.